This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No.P2001-271168, filed Sep. 7, 2001; the entire contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a fusion splicing method and device for optical fibers, specifically, ribbon optical fibers (having a tape-shaped structure) capable of obtaining a good splice state of the ribbon optical fibers by controlling the interval between discharge electrode rods according to the number of the bare fibers in the fusing and splicing process.
2. Description of the Related Art
In a fusing splicing process for optical fibers, specifically, ribbon optical fibers having a tape-shaped structure, the bare fibers (which are distal ends of the optical fibers, each bare fiber is made up of a core and a cladding where a coated material has been eliminated) to be spliced together are arranged and aligned, in opposite direction to each other, in V-grooves formed on a V-groove block in a fiber setup stage. Then, an aerial discharge (arc discharge) is generated between a pair of electrode rods. The bare fibers of the ribbon optical fibers are thereby fused and spliced together. This is called a fusing splicing method.
In a fusion splicing device performing such a general fusion splicing process of a related art, the interval between a pair of the discharge electrode rods is fixed. That is, the interval between the discharge electrode rods is set to a constant interval.
In order to accommodate various ribbon optical fibers having a different number of optical fibers, for example, as shown in FIG. 1, the interval between the discharge electrode rods 1 and 2 is set to an optimum length by which a discharge area has an optimum distribution for the optical fibers during an aerial discharge based on various parameters such as a distance xcex4 a from the discharge electrode rod 1 to the left side of the bare fibers xe2x80x9cfxe2x80x9d, a distance xcex4 b from the discharge electrode rod 2 to the right side of the bare fibers xe2x80x9cfxe2x80x9d, and an offset value xcex4 c between the height of a center position of each of the electrode rods 1 and 2 and the center position of each bare fiber xe2x80x9cfxe2x80x9d.
Following is the reason why it is necessary to perform the control described above. For example, as shown in FIG. 2, when an arc discharge occurs between a pair of the discharge electrode rods 1 and 2 in the atmosphere under a normal condition, the distribution of temperature in the discharge area 3 is symmetric between the upper and lower halves, and a rapid temperature change occurs around the discharge electrode rods 1 and 2. On the contrary, an area, which is separated in position from a pair of the discharge electrode rods 1 and 2, has a relatively uniform and wide temperature area.
In an actual fusion splicing process, it is necessary to control that a relatively uniform and wide temperature area is detected according to the number of ribbon optical fibers to be spliced together, and all of the bare fibers of the ribbon optical fibers are then set in this uniform temperature area in order to heat all of the bare fibers at the uniform temperature.
However, when the number of the optical fibers (fiber number) is increased, the width of the ribbon optical fiber of a tape-shaped structure is increased. Accordingly, it becomes difficult to detect the uniform temperature area in the discharge area 3 generated between the electrode rods 1 and 2, and further to set all of the bare fibers xe2x80x9cfxe2x80x9d in this uniform temperature area in order to heat them at the uniform temperature.
For example, when the number of the bare fibers is within a range of 1-12, even if the electrode rods 1 and 2 whose position is fixed are used, it is possible to set all of the bare fibers in the discharge area 3 caused between the discharge electrode rods 1 and 2 by setting those parameters to optimum values. However, when the number of the bare fibers is within 13-18, and further within 19-24, it becomes difficult to heat all of the bare fibers at a uniform temperature.
That is, when the number of optical fibers is increased, it is necessary to increase an amount of heat obtained by the discharge according to the increasing of the number of the optical fibers, and also to increase an electric power for the discharge. However, it is difficult to set the optimum discharge power based on the number of the optical fibers.
In various fusion splicing devices of the related art, when the interval between the discharge electrode rods 1 and 2 is changed according to a ribbon optical fiber having the maximum number of the optical fibers, there is a drawback that it is difficult for a non-skilled operator to detect a shape of the distribution of the discharge area, to obtain the optimum discharge power by determining the optimum interval between the discharge electrode rods.
Further, there is a following drawback in the related art. Even if the fusion splicing device having a fixed interval between the discharge electrode rods is used, where this fixed interval corresponds to a ribbon optical fiber having the maximum fiber number, it becomes difficult to obtain a stable amount of heat to perform the splicing fusion process for ribbon optical fibers whose number of optical fibers is small.
Accordingly, an object of the present invention is, with due consideration to the drawbacks of the related technique, to provide a fusion splicing method and device for optical fibers in which an interval between discharge electrode rods is changeable, namely determined, according to the number of optical fibers of an optical fiber, specifically, a ribbon optical fiber. For example, according to various ranges of fiber numbers, that have been set in advance, the interval between the discharge electrode rods is controlled in order to generate the discharge area having the optimum discharge power. Thereby, it is possible to heat all of bare fibers of the ribbon optical fibers at a uniform temperature, and thereby to obtain a good splice state of all of the bare fibers of the ribbon optical fibers.
According to an embodiment, a fusion splicing method for optical fibers has following steps: arranging bare fibers of ribbon optical fibers to be spliced together, in opposite direction to each other, on a fiber setup stage; and performing a discharge between a pair of discharge electrode rods by changing an interval between a pair of the discharge electrode rods according to a fiber number of the ribbon optical fibers so that all of the bare fibers are set in a uniform temperature area in the discharge, and fusing and splicing the bare fibers together.
In addition, according to another embodiment, a fusion splicing device for optical fibers has a fiber setup stage on which ribbon optical fibers to be spliced together are arranged in opposite direction to each other, and a pair of discharge electrode rods for generating a discharge between them in order to fuse and splice the ribbon optical fibers arranged on the fiber setup stage. In the fusion splicing device, in order to set all of bare fibers of the ribbon optical fibers into a uniform temperature area in a discharge generated between the discharge electrode rods, one of or both the discharge electrode rods are shifted by a predetermined length according to a fiber number of the ribbon optical fibers, and the ribbon optical fibers are fused and spliced together based on the interval obtained between the discharge electrode rods.
Still further, according to another embodiment, a fusion splicing device for optical fibers has a fiber setup stage on which ribbon optical fibers to be spliced together are arranged in opposite direction to each other, and a plurality of discharge electrode rods of different lengths, each length corresponding to each fiber-number class of the ribbon optical fiber, where each fiber-number class being set corresponding to a fiber number of each ribbon optical fiber. In the fusion splicing device, one pair of the discharge electrode rods of different lengths is selected according to the fiber-number class corresponding to the fiber number of the ribbon optical fibers to be spliced together, and the fusion splicing process is performed by setting the optimum discharge interval by using the selected discharge electrode rods.
The above and other features and advantages of this invention and the manner of realizing them will become more apparent, and the invention itself will best be understood, from a study of the following description and attached claims, with reference had to the attached drawings showing some preferable embodiments of the invention.